Relaxing to a cable rerun of "Seinfeld"? The break includes a message from seniors who fret about their Social Security benefits if Republican Ken Buck is elected.

It's not just commercials. Coloradoans drive by one billboard after another, carrying political messages, before arriving home to a mailbox full of pleas from politicians.

Shadowy out-of-state interest groups have been flooding Colorado with a level of advertising that goes well beyond the typical election year bombardment. Colorado has become such an attractive destination for outside political money this year because of the state's bellwether status, its many competitive races and its relatively cheap media rates.

The top target is the Senate contest between Bennet and Buck, a race that could help determine the control of Congress. Competitive House races in the state have also been affected by the spending.

Among the heavy-hitters coming to Buck's assistance is American Crossroads, a conservative group affiliated with Republican strategist Karl Rove that has spent almost $2.6 million on ads attacking Bennet.

An affiliated group, Crossroads Grassroots Policy Strategies, has spent more than $213,000 against Bennet. On Tuesday, two watchdog groups filed complaints with the IRS against Crossroads GPS, arguing the group has violated campaigning rules under its tax-exempt status.

According to the Sunlight Foundation, a Washington-based watchdog group that tracks campaign finance, most of the outside spending in Colorado is coming from groups aligned with the GOP.

Most of the attacks on Buck are coming from the Democratic Senatorial Campaign Committee, which has poured $3.1 million into attack ads.

One of the few Democratic allies attacking Buck is Campaign Money Watch, which spent some $750,000 this week on an ad blasting Buck for a reprimand he received a decade ago for discussing a case as a federal prosecutor. The ad calls Buck "just plain wrong for Colorado."

People are scratching their heads at all the outside attention Colorado has drawn. In rural eastern Colorado, 67-year-old Democratic volunteer Jim Bowen talks politics with his friends at a Prowers County senior center and is amazed how much advertising they're getting.

"People are confused, and I don't blame them," said Bowen, a retired postmaster. "It's just amazing, the lack of accurate information that goes out."

Republicans are voicing similar opinions. Nathan Hatcher, a Republican volunteer in the Denver suburb of Arvada, said that heavy outside spending in Colorado this year has overwhelmed traditional neighbor-to-neighbor outreach.

"These ads, they scare people," Hatcher said. "One of my daughter's friends was talking about one of these ads, and she's 12. I mean, what is going on? It's both sides doing it, and it seems like there's no way to stop it."

Why Colorado? Analysts say the avalanche of campaign spending has largely been prompted by close races and a Supreme Court ruling earlier this year that loosened campaign restrictions on businesses.

"Corporations are now free to spend unlimited amounts of money on campaigning," said Paul Ryan, an elections law expert with the Campaign Legal Center, one of the groups that filed a complaint against Crossroads GPS. "It's a green light to get involved in a politics and spend whatever you want."

Colorado is also an attractive state for outside spending because the state has just about 5 million people, some 70 percent of them reachable by advertisements on Denver TV stations. That means a dollar spent in Colorado has more impact than a dollar spent in states with multiple big-city markets.

Bennet has been questioning the outside groups financing attack ads against him.

"It's unprecedented in Colorado," Bennet said. "Colorado's become ground zero for Karl Rove and (conservative South Carolina Sen.) Jim DeMint to play with the voters. I think Colorado voters want this to be about Colorado."

Buck, the beneficiary of so much outside spending, shrugged off suggestions that the Bennet-bashing coming from out of state will make the difference.

"I think what voters care about is the authenticity and the general message coming from the candidate and not all these outside groups," Buck said.

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